Protected active metal electrode and battery cell with ionically conductive preotective architecture

ABSTRACT

Active metal and active metal intercalation electrode structures and battery cells having ionically conductive protective architecture including an active metal (e.g., lithium) conductive impervious layer separated from the electrode (anode) by a porous separator impregnated with a non-aqueous electrolyte (anolyte). This protective architecture prevents the active metal from deleterious reaction with the environment on the other (cathode) side of the impervious layer, which may include aqueous or non-aqueous liquid electrolytes (catholytes) and/or a variety electrochemically active materials, including liquid, solid and gaseous oxidizers. Safety additives and designs that facilitate manufacture are also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/824,597, filed Jun. 28, 2007, titled PROTECTED ACTIVE METAL ELECTRODEAND BATTERY CELL STRUCTURES WITH NON-AQUEOUS INTERLAYER ARCHITECTURE,now pending; which is a divisional of U.S. patent application Ser. No.10/824,944, filed Apr. 14, 2004, titled PROTECTED ACTIVE METAL ELECTRODEAND BATTERY CELL STRUCTURES WITH NON-AQUEOUS INTERLAYER ARCHITECTURE,now U.S. Pat. No. 7,282,295; which in turn claims priority to U.S.Provisional Patent Application No. 60/542,532 filed Feb. 6, 2004, titledPROTECTED ACTIVE METAL ELECTRODE AND BATTERY CELL STRUCTURES WITHNON-AQUEOUS INTERLAYER ARCHITECTURE; and U.S. Provisional PatentApplication No. 60/548,231 filed Feb. 27, 2004, titled VARIATIONS ONPROTECTED ACTIVE METAL ELECTRODE AND BATTERY CELL STRUCTURES WITHNON-AQUEOUS INTERLAYER ARCHITECTURE; the disclosures of which areincorporated herein by reference in their entirety and for all purposes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to active metal electrochemicaldevices. More particularly, this invention relates to an active metal(e.g., alkali metals, such as lithium), active metal intercalation (e.g.lithium-carbon, carbon) and active metal alloys (e.g., lithium-tin)alloys or alloying metals (e.g., tin) electrochemical (e.g., electrode)structures and battery cells. The electrode structures have ionicallyconductive protective architecture including an active metal (e.g.,lithium) conductive impervious layer separated from the electrode(anode) by a porous separator impregnated with a non-aqueouselectrolyte. This protective architecture prevents the active metal fromdeleterious reaction with the environment on the other (cathode) side ofthe impervious layer, which may include aqueous, air or organic liquidelectrolytes and/or electrochemically active materials.

2. Description of Related Art

The low equivalent weight of alkali metals, such as lithium, render themparticularly attractive as a battery electrode component. Lithiumprovides greater energy per volume than the traditional batterystandards, nickel and cadmium. Unfortunately, no rechargeable lithiummetal batteries have yet succeeded in the market place.

The failure of rechargeable lithium metal batteries is largely due tocell cycling problems. On repeated charge and discharge cycles, lithium“dendrites” gradually grow out from the lithium metal electrode, throughthe electrolyte, and ultimately contact the positive electrode. Thiscauses an internal short circuit in the battery, rendering the batteryunusable after a relatively few cycles. While cycling, lithiumelectrodes may also grow “mossy” deposits that can dislodge from thenegative electrode and thereby reduce the battery's capacity.

To address lithium's poor cycling behavior in liquid electrolytesystems, some researchers have proposed coating the electrolyte facingside of the lithium negative electrode with a “protective layer.” Suchprotective layer must conduct lithium ions, but at the same time preventcontact between the lithium electrode surface and the bulk electrolyte.Many techniques for applying protective layers have not succeeded.

Some contemplated lithium metal protective layers are formed in situ byreaction between lithium metal and compounds in the cell's electrolytethat contact the lithium. Most of these in situ films are grown by acontrolled chemical reaction after the battery is assembled. Generally,such films have a porous morphology allowing some electrolyte topenetrate to the bare lithium metal surface. Thus, they fail toadequately protect the lithium electrode.

Various pre-formed lithium protective layers have been contemplated. Forexample, U.S. Pat. No. 5,314,765 (issued to Bates on May 24, 1994)describes an ex situ technique for fabricating a lithium electrodecontaining a thin layer of sputtered lithium phosphorus oxynitride(“LiPON”) or related material. LiPON is a glassy single ion conductor(conducts lithium ion) that has been studied as a potential electrolytefor solid state lithium microbatteries that are fabricated on siliconand used to power integrated circuits (See U.S. Pat. Nos. 5,597,660,5,567,210, 5,338,625, and 5,512,147, all issued to Bates et al.).

Work in the present applicants' laboratories has developed technologyfor the use of glassy or amorphous protective layers, such as LiPON, inactive metal battery electrodes. (See, for example, U.S. Pat. Nos.6,025,094, issued Feb. 15, 2000, 6,402,795, issued Jun. 11, 2002,6,214,061, issued Apr. 10, 2001 and 6,413,284, issued Jul. 2, 2002, allassigned to PolyPlus Battery Company).

Prior attempts to use lithium anodes in aqueous environments reliedeither on the use of very basic conditions such as use of concentratedaqueous KOH to slow down the corrosion of the Li electrode, or on theuse of polymeric coatings on the Li electrode to impede the diffusion ofwater to the Li electrode surface. In all cases however, there wassubstantial reaction of the alkali metal electrode with water. In thisregard, the prior art teaches that the use of aqueous cathodes orelectrolytes with Li-metal anodes is not possible since the breakdownvoltage for water is about 1.2 V and a Li/water cell can have a voltageof about 3.0 V. Direct contact between lithium metal and aqueoussolutions results in violent parasitic chemical reaction and corrosionof the lithium electrode for no useful purpose. Thus, the focus ofresearch in the lithium metal battery field has been squarely on thedevelopment of effective non-aqueous (mostly organic) electrolytesystems.

SUMMARY OF THE INVENTION

The present invention relates generally to active metal electrochemicaldevices. More particularly, this invention relates to an active metal(e.g., alkali metals, such as lithium), active metal intercalation (e.g.lithium-carbon, carbon) and active metal alloys (e.g., lithium-tin)alloys or alloying metals (e.g., tin) electrochemical (e.g., electrode)structures and battery cells. The electrochemical structures haveionically conductive protective architecture including an active metal(e.g., lithium) ion conductive substantially impervious layer separatedfrom the electrode (anode) by a porous separator impregnated with anon-aqueous electrolyte (anolyte). This protective architecture preventsthe active metal from deleterious reaction with the environment on theother (cathode) side of the impervious layer, which may include aqueous,air or organic liquid electrolytes (catholytes) and/or electrochemicallyactive materials.

The separator layer of the protective architecture prevents deleteriousreaction between the active metal (e.g., lithium) of the anode and theactive metal ion conductive substantially impervious layer. Thus, thearchitecture effectively isolates (de-couples) the anode/anolyte fromsolvent, electrolyte processing and/or cathode environments, includingsuch environments that are normally highly corrosive to Li or otheractive metals, and at the same time allows ion transport in and out ofthese potentially corrosive environments.

Various embodiments of the cells and cell structures of the presentinvention include active metal, active metal-ion, active metal alloyingmetal, and active metal intercalating anode materials protected with anionically conductive protective architecture having a non-aqueousanolyte. These anodes may be combined in battery cells with a variety ofpossible cathode systems, including water, air, metal hydride and metaloxide cathodes and associated catholyte systems, in particular aqueouscatholyte systems.

Safety additives may also be incorporated into the structures and cellsof the present invention for the case where the substantially imperviouslayer of the protective architecture (e.g., a glass or glass-ceramicmembrane) cracks or otherwise breaks down and allows the aggressivecatholyte to enter and approach the lithium electrode. The non-aqueousinterlayer architecture can incorporate a gelling/polymerizing agentthat, when in contact with the reactive catholyte, leads to theformation of an impervious polymer on the lithium surface. For example,the anolyte may include a monomer for a polymer that is insoluble orminimally soluble in water, for example dioxolane (Diox)/polydioxaloaneand the catholyte may include a polymerization initiator for themonomer, for example, a protonic acid.

In addition, the structures and cells of the present invention may takeany suitable form. One advantageous form that facilitates fabrication isa tubular form.

In one aspect, the invention pertains to an electrochemical cellstructure. The structure includes an anode composed of an active metal,active metal-ion, active metal alloy, active metal alloying metal oractive metal intercalating material. The anode has an ionicallyconductive protective architecture on its surface. The architectureincludes an active metal ion conducting separator layer that has anon-aqueous anolyte and is chemically compatible with the active metaland in contact with the anode, and a substantially impervious ionicallyconductive layer chemically compatible with the separator layer andaqueous environments and in contact with the separator layer. Theseparator layer may be, a semi-permeable membrane impregnated with anorganic anolyte, for example, a micro-porous polymer impregnated with aliquid or gel phase anolyte. Such an electrochemical (electrode)structure may be paired with a cathode system, including an aqueouscathode system, to form battery cells in accordance with the presentinvention.

The structures and battery cells incorporating the structures of thepresent invention may have various configurations, including prismaticand cylindrical, and compositions, including active metal ion, alloy andintercalation anodes, aqueous, water, air, metal hydride and metal oxidecathodes, and aqueous, organic or ionic liquid catholytes; electrolyte(anolyte and/or catholyte) compositions to enhance the safety and/orperformance of the cells; and fabrication techniques.

These and other features of the invention are further described andexemplified in the detailed description below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an electrochemical structure cellincorporating an ionically conductive protective interlayer architecturein accordance with the present invention.

FIG. 2 is a schematic illustration of a battery cell incorporating anionically conductive protective interlayer architecture in accordancewith the present invention.

FIGS. 3A-C illustrate embodiments of battery cells in accordance withthe present invention that use a tubular protected anode design.

FIGS. 4-6 are plots of data illustrating the performance of variouscells incorporating anodes with ionically conductive protectiveinterlayer architecture in accordance with the present invention.

FIG. 7 illustrates a Li/water battery and hydrogen generator for a fuelcell in accordance with one embodiment of the present invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Reference will now be made in detail to specific embodiments of theinvention. Examples of the specific embodiments are illustrated in theaccompanying drawings. While the invention will be described inconjunction with these specific embodiments, it will be understood thatit is not intended to limit the invention to such specific embodiments.On the contrary, it is intended to cover alternatives, modifications,and equivalents as may be included within the spirit and scope of theinvention as defined by the appended claims. In the followingdescription, numerous specific details are set forth in order to providea thorough understanding of the present invention. The present inventionmay be practiced without some or all of these specific details. In otherinstances, well known process operations have not been described indetail in order not to unnecessarily obscure the present invention.

When used in combination with “comprising,” “a method comprising,” “adevice comprising” or similar language in this specification and theappended claims, the singular forms “a,” “an,” and “the” include pluralreference unless the context clearly dictates otherwise. Unless definedotherwise, all technical and scientific terms used herein have the samemeaning as commonly understood to one of ordinary skill in the art towhich this invention belongs.

INTRODUCTION

Active metals are highly reactive in ambient conditions and can benefitfrom a barrier layer when used as electrodes. They are generally alkalimetals such (e.g., lithium, sodium or potassium), alkaline earth metals(e.g., calcium or magnesium), and/or certain transitional metals (e.g.,zinc), and/or alloys of two or more of these. The following activemetals may be used: alkali metals (e.g., Li, Na, K), alkaline earthmetals (e.g., Ca, Mg, Ba), or binary or ternary alkali metal alloys withCa, Mg, Sn, Ag, Zn, Bi, Al, Cd, Ga, In. Preferred alloys include lithiumaluminum alloys, lithium silicon alloys, lithium tin alloys, lithiumsilver alloys, and sodium lead alloys (e.g., Na₄Pb). A preferred activemetal electrode is composed of lithium.

The low equivalent weight of alkali metals, such as lithium, render themparticularly attractive as a battery electrode component. Lithiumprovides greater energy per volume than the traditional batterystandards, nickel and cadmium. However, lithium metal or compoundsincorporating lithium with a potential near that (e.g., within about avolt) of lithium metal, such as lithium alloy and lithium-ion (lithiumintercalation) anode materials, are highly reactive to many potentiallyattractive electrolyte and cathode materials. This invention describesthe use of a non-aqueous electrolyte interlayer architecture to isolatean active metal (e.g., alkali metal, such as lithium), active metalalloy or active metal-ion electrode (usually the anode of a batterycell) from ambient and/or the cathode side of the cell. The architectureincludes an active metal ion conducting separator layer with anon-aqueous anolyte (i.e., electrolyte about the anode), the separatorlayer being chemically compatible with the active metal and in contactwith the anode, and a substantially impervious ionically conductivelayer chemically compatible with the separator layer and aqueousenvironments and in contact with the separator layer. The non-aqueouselectrolyte interlayer architecture effectively isolates (de-couples)the anode from ambient and/or cathode, including catholyte (i.e.,electrolyte about the cathode) environments, including such environmentsthat are normally highly corrosive to Li or other active metals, and atthe same time allows ion transport in and out of these potentiallycorrosive environments. In this way, a great degree of flexibility ispermitted the other components of an electrochemical device, such as abattery cell, made with the architecture. Isolation of the anode fromother components of a battery cell or other electrochemical cell in thisway allows the use of virtually any solvent, electrolyte and/or cathodematerial in conjunction with the anode. Also, optimization ofelectrolytes or cathode-side solvent systems may be done withoutimpacting anode stability or performance.

There are a variety of applications that could benefit from the use ofaqueous solutions, including water and water-based electrolytes, air,and other materials reactive to lithium and other active metals,including organic solvents/electrolytes and ionic liquids, on thecathode side of the cell with an active (e.g., alkali, e.g., lithium)metal or active metal intercalation (e.g., lithium alloy or lithium-ion)anode in a battery cell.

The use of lithium intercalation electrode materials like lithium-carbonand lithium alloy anodes, rather than lithium metal, for the anode canalso provide beneficial battery characteristics. First of all, it allowsthe achievement of prolonged cycle life of the battery without risk offormation of lithium metal dendrites that can grow from the Li surfaceto the membrane surface causing the membrane's deterioration. Also, theuse of lithium-carbon and lithium alloy anodes in some embodiments ofthe present invention instead of lithium metal anode can significantlyimprove a battery's safety because it avoids formation of highlyreactive “mossy” lithium during cycling.

The present invention describes a protected active metal, alloy orintercalation electrode that enables very high energy density lithiumbatteries such as those using aqueous electrolytes or other electrolytesthat would otherwise adversely react with lithium metal, for example.Examples of such high energy battery couples are lithium-air,lithium-water lithium-metal hydride, lithium-metal oxide, and thelithium alloy and lithium-ion variants of these. The cells of theinvention may incorporate additional components in their electrolytes(anolytes and catholytes) to enhance cell safety, and may have a varietyof configurations, including planar and tubular/cylindrical.

Non-Aqueous Interlayer Architecture

The non-aqueous interlayer architecture of the present invention isprovided in an electrochemical cell structure, the structure having ananode composed of a material selected from the group consisting ofactive metal, active metal-ion, active metal alloy, active metalalloying and active metal intercalating material, and an ionicallyconductive protective architecture on a first surface of the anode. Thearchitecture is composed of an active metal ion conducting separatorlayer with a non-aqueous anolyte, the separator layer being chemicallycompatible with the active metal and in contact with the anode, and asubstantially impervious ionically conductive layer chemicallycompatible with the separator layer and aqueous environments and incontact with the separator layer. The separator layer may include asemi-permeable membrane, for example, a micro-porous polymer, such asare available from Celgard, Inc. Charlotte, N.C., impregnated with anorganic anolyte.

The protective architecture of this invention incorporates asubstantially impervious layer of an active metal ion conducting glassor glass-ceramic (e.g., a lithium ion conductive glass-ceramic (LIC-GC))that has high active metal ion conductivity and stability to aggressiveelectrolytes that vigorously react with lithium metal, for example) suchas aqueous electrolytes. Suitable materials are substantiallyimpervious, ionically conductive and chemically compatible with aqueouselectrolytes or other electrolyte (catholyte) and/or cathode materialsthat would otherwise adversely react with lithium metal, for example.Such glass or glass-ceramic materials are substantially gap-free,non-swellable and are inherently ionically conductive. That is, they donot depend on the presence of a liquid electrolyte or other agent fortheir ionically conductive properties. They also have high ionicconductivity, at least 10⁻⁷ S/cm, generally at least 10⁻⁶ S/cm, forexample at least 10⁻⁵ S/cm to 10⁻⁴ S/cm, and as high as 10⁻³ S/cm orhigher so that the overall ionic conductivity of the multi-layerprotective structure is at least 10⁻⁷ S/cm and as high as 10⁻³ S/cm orhigher. The thickness of the layer is preferably about 0.1 to 1000microns, or, where the ionic conductivity of the layer is about 10⁻⁷S/cm, about 0.25 to 1 micron, or, where the ionic conductivity of thelayer is between about 10⁻⁴ about 10⁻³ S/cm, about 10 to 1000 microns,preferably between 1 and 500 microns, and more preferably between 10 and100 microns, for example 20 microns.

Suitable examples of suitable substantially impervious lithium ionconducting layers include glassy or amorphous metal ion conductors, suchas a phosphorus-based glass, oxide-based glass,phosphorus-oxynitride-based glass, sulpher-based glass, oxide/sulfidebased glass, selenide based glass, gallium based glass, germanium-basedglass or boracite glass (such as are described D. P. Button et al.,Solid State Ionics, Vols. 9-10, Part 1, 585-592 (December 1983); ceramicactive metal ion conductors, such as lithium beta-alumina, sodiumbeta-alumina, Li superionic conductor (LISICON), Na superionic conductor(NASICON), and the like; or glass-ceramic active metal ion conductors.Specific examples include LiPON, Li₃PO₄·Li₂S·SiS₂, Li₂S·GeS₂·Ga₂S₃,Li₂O·11Al₂O₃, Na₂O·11Al₂O₃, (Na, Li)_(1+x)Ti_(2−x)Al_(x)(PO₄)₃(0.6≦×≦0.9) and crystallographically related structures, Na₃Zr₂Si₂PO₁₂,Li₃Zr₂Si₂PO₁₂, Na₅ZrP₃O₁₂, Na₅TiP₃O₁₂, Na₃Fe₂P₃O₁₂, Na₄NbP₃O₁₂,Li₅ZrP₃O₁₂, Li₅TiP₃O₁₂, Li₃Fe₂P₃O₁₂ and Li₄NbP₃O₁₂, and combinationsthereof, optionally sintered or melted. Suitable ceramic ion activemetal ion conductors are described, for example, in U.S. Pat. No.4,985,317 to Adachi et al., incorporated by reference herein in itsentirety and for all purposes.

A particularly suitable glass-ceramic material for the substantiallyimpervious layer of the protective architecture is a lithium ionconductive glass-ceramic having the following composition:

Composition mol % P₂O₅ 26-55% SiO₂ 0-15% GeO₂ + TiO₂ 25-50% in whichGeO₂ 0-50% TiO₂ 0-50% ZrO₂ 0-10% M₂O₃ 0-10% Al₂O₃ 0-15% Ga₂O₃ 0-15% Li₂O3-25%and containing a predominant crystalline phase composed ofLi_(1+x)(M,Al,Ga)_(x)(Ge_(1−y)Ti_(y))_(2−x)(PO₄)₃ where X≦0.8 and0≦Y≦1.0, and where M is an element selected from the group consisting ofNd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb, and/orLi_(1+x+y)Q_(x)Ti_(2−x)Si_(y)P_(3−y)O₁₂ where 0<X≦0.4 and 0<Y≦0.6, andwhere Q is Al or Ga. The glass-ceramics are obtained by melting rawmaterials to a melt, casting the melt to a glass and subjecting theglass to a heat treatment. Such materials are available from OHARACorporation, Japan and are further described in U.S. Pat. Nos.5,702,995, 6,030,909, 6,315,881 and 6,485,622, incorporated herein byreference.

Such lithium ion conductive substantially impervious layers andtechniques for their fabrication and incorporation in battery calls aredescribed in U.S. Provisional Patent Application No. 60/418,899, filedOct. 15, 2002, titled IONICALLY CONDUCTIVE COMPOSITES FOR PROTECTION OFANODES AND ELECTROLYTES, its corresponding U.S. patent application Ser.No. 10/686,189 (Attorney Docket No. PLUSP027), filed Oct. 14, 2003, andtitled IONICALLY CONDUCTIVE COMPOSITES FOR PROTECTION OF ACTIVE METALANODES, U.S. patent application Ser. No. 10/731,771 (Attorney Docket No.PLUSP027), filed Dec. 5, 2003, and titled IONICALLY CONDUCTIVECOMPOSITES FOR PROTECTION OF ACTIVE METAL ANODES, and U.S. patentapplication Ser. No. 10/772,228 (Attorney Docket No. PLUSP039), filedFeb. 3, 2004, and titled IONICALLY CONDUCTIVE MEMBRANES FOR PROTECTIONOF ACTIVE METAL ANODES AND BATTERY CELLS. These applications areincorporated by reference herein in their entirety for all purposes.

A critical limitation in the use of these highly conductive glasses andglass-ceramics in lithium (or other active metal or active metalintercalation) batteries is their reactivity to lithium metal orcompounds incorporating lithium with a potential near that (e.g., withinabout a volt) of lithium metal. The non-aqueous electrolyte interlayerof the present invention isolates the lithium (for example) electrodefrom reacting with the glass or glass-ceramic membrane. The non-aqueousinterlayer may have a semi-permeable membrane, such as a Celgardmicro-porous separator, to prevent mechanical contact of the lithiumelectrode to the glass or glass-ceramic membrane. The membrane isimpregnated with organic liquid electrolyte (anolyte) with solvents suchas ethylene carbonate (EC), propylene carbonate (PC), 1,2-dimethoxyethane (DME),1,3-dioxolane (DIOX), or various ethers, glymes, lactones,sulfones, sulfolane, or mixtures thereof. It may also or alternativelyhave a polymer electrolyte, a gel-type electrolyte, or a combination ofthese. The important criteria are that the lithium electrode is stablein the non-aqueous anolyte, the non-aqueous anolyte is sufficientlyconductive to Li⁺ ions, the lithium electrode does not directly contactthe glass or glass-ceramic membrane, and the entire assembly allowslithium ions to pass through the glass or glass-ceramic membrane.

Referring to FIG. 1, a specific embodiment of the present invention isillustrated and described. FIG. 1 shows an unsealed depiction of anelectrochemical cell structure 100 having an active metal, activemetal-ion, active metal alloying metal, or active metal intercalatingmaterial anode 102 and an ionically conductive protective architecture104. The protective architecture 104 has an active metal ion conductingseparator layer 106 with a non-aqueous anolyte (sometimes also referredto as a transfer electrolyte) on a surface of the anode 102 and asubstantially impervious ionically conductive layer 108 in contact withthe separator layer 106. The separator layer 106 is chemicallycompatible with the active metal and the substantially impervious layer108 is chemically compatible with the separator layer 106 and aqueousenvironments. The structure 100 may optionally include a currentcollector 110, composed of a suitable conductive metal that does notalloy with or intercalate the active metal. When the active metal islithium, a suitable current collector material is copper. The currentcollector 110 can also serve to seal the anode from ambient to preventdeleterious reaction of the active metal with ambient air or moisture.

The separator layer 106 is composed of a semi-permeable membraneimpregnated with an organic anolyte. For example, the semi-permeablemembrane may be a micro-porous polymer, such as are available fromCelgard, Inc. The organic anolyte may be in the liquid or gel phase. Forexample, the anolyte may include a solvent selected from the groupconsisting of organic carbonates, ethers, lactones, sulfones, etc, andcombinations thereof, such as EC, PC, DEC, DMC, EMC, 1,2-DME or higherglymes, THF, 2MeTHF, sulfolane, and combinations thereof. 1,3-dioxolanemay also be used as an anolyte solvent, particularly but not necessarilywhen used to enhance the safety of a cell incorporating the structure,as described further below. When the anolyte is in the gel phase,gelling agents such as polyvinylidine fluoride (PVdF) compounds,hexafluoropropylene-vinylidene fluoride copolymers (PVdf-HFP),polyacrylonitrile compounds, cross-linked polyether compounds,polyalkylene oxide compounds, polyethylene oxide compounds, andcombinations and the like may be added to gel the solvents. Suitableanolytes will also, of course, also include active metal salts, such as,in the case of lithium, for example, LiPF₆, LiBF₄, LiAsF₆, LiSO₃CF₃ orLiN(SO₂C₂F₅)₂. One example of a suitable separator layer is 1 M LiPF₆dissolved in propylene carbonate and impregnated in a Celgardmicroporous polymer membrane.

There are a number of advantages of a protective architecture inaccordance with the present invention. In particular, cell structuresincorporating such an architecture may be relatively easilymanufactured. In one example, lithium metal is simply placed against amicro-porous separator impregnated with organic liquid or gelelectrolyte and with the separator adjacent to a glass/glass ceramicactive metal ion conductor.

An additional advantage of the non-aqueous interlayer is realized whenglass-ceramics are used. When amorphous glasses of the type described bythe OHARA Corp. patents cited above are heat-treated, the glassdevitrifies, leading to the formation of a glass-ceramic. However, thisheat treatment can lead to the formation of surface roughness which maybe difficult to coat using vapor phase deposition of an inorganicprotective interlayer such as LiPON, Cu₃N, etc. The use of a liquid (orgel), non-aqueous electrolyte interlayer would easily cover such a roughsurface by normal liquid flow, thereby eliminating the need for surfacepolishing, etc. In this sense, techniques such as “draw-down” (asdescribed by Sony Corporation and Shott Glass (T. Kessler, H. Wegener,T. Togawa, M. Hayashi, and T. Kakizaki, “Large Microsheet Glass for40-in. Class PALC Displays,” 1997, FMC2-3, downloaded from Shott Glasswebsite; http://www.schott.com/english, incorporated herein byreference) could be used to form thin glass layers (20 to 100 microns),and these glasses heat treated to form glass-ceramics.

Battery Cells

The non-aqueous interlayer architecture is usefully adopted in batterycells. For example, the electrochemical structure 100 of FIG. 1 can bepaired with a cathode system 120 to form a cell 200, as depicted in FIG.2. The cathode system 120 includes an electronically conductivecomponent, an ionically conductive component, and an electrochemicallyactive component. The cathode system 120 may have any desiredcomposition and, due to the isolation provided by the protectivearchitecture, is not limited by the anode or anolyte composition. Inparticular, the cathode system may incorporate components which wouldotherwise be highly reactive with the anode active metal, such asaqueous materials, including water, aqueous catholytes and air, metalhydride electrodes and metal oxide electrodes.

In one embodiment, a Celgard separator would be placed against one sideof the thin glass-ceramic, followed by a non-aqueous liquid or gelelectrolyte, and then a lithium electrode. On the other side of theglass ceramic membrane, an aggressive solvent could be used, such as anaqueous electrolyte. In such a way, an inexpensive Li/water or Li/aircell, for example, could be built.

Cathode Systems

As noted above, the cathode system 120 of a battery cell in accordancewith the present invention may have any desired composition and, due tothe isolation provided by the protective architecture, is not limited bythe anode or anolyte composition. In particular, the cathode system mayincorporate components which would otherwise be highly reactive with theanode active metal, such as aqueous materials, including water, aqueoussolutions and air, metal hydride electrodes and metal oxide electrodes.

Battery cells of the present invention may include, without limitation,water, aqueous solutions, air electrodes and metal hydride electrodes,such as are described in co-pending application Ser. No. 10/772,157titled ACTIVE METAL/AQUEOUS ELECTROCHEMICAL CELLS AND SYSTEMS, now U.S.Pat. No. 7,645,543, incorporated herein by reference in its entirety andfor all purposes, and metal oxide electrodes, as used, for example, inconventional Li-ion cells.

The effective isolation between anode and cathode achieved by theprotective interlayer architecture of the present invention also enablesa great degree of flexibility in the choice of catholyte systems, inparticular aqueous systems, but also non-aqueous systems. Since theprotected anode is completely decoupled from the catholyte, so thatcatholyte compatibility with the anode is no longer an issue, solventsand salts which are not kinetically stable to Li can be used.

For cells using water as an electrochemically active cathode material, aporous electronically conductive support structure can provide theelectronically conductive component of the cathode system. An aqueouselectrolyte (catholyte) provides ion carriers for transport(conductivity) of Li ions and anions that combine with Li. Theelectrochemically active component (water) and the ionically conductivecomponent (aqueous catholyte) will be intermixed as a single solution,although they are conceptually separate elements of the battery cell.Suitable catholytes for the Li/water battery cell of the inventioninclude any aqueous electrolyte with suitable ionic conductivity.Suitable electrolytes may be acidic, for example, strong acids like HCl,H₂SO₄, H₃PO₄ or weak acids like acetic acid/Li acetate; basic, forexample, LiOH; neutral, for example, sea water, LiCl, LiBr, LiI; oramphoteric, for example, NH₄Cl, NH₄Br, etc

The suitability of sea water as an electrolyte enables a battery cellfor marine applications with very high energy density. Prior to use, thecell structure is composed of the protected anode and a porouselectronically conductive support structure (electronically conductivecomponent of the cathode). When needed, the cell is completed byimmersing it in sea water which provides the electrochemically activeand ionically conductive components. Since the latter components areprovided by the sea water in the environment, they need not transportedas part of the battery cell prior to it use (and thus need not beincluded in the cell's energy density calculation). Such a cell isreferred to as an “open” cell since the reaction products on the cathodeside are not contained. Such a cell is, therefore, a primary cell.

Secondary Li/water cells are also possible in accordance with theinvention. As noted above, such cells are referred to as “closed” cellssince the reaction products on the cathode side are contained on thecathode side of the cell to be available to recharge the anode by movingthe Li ions back across the protective membrane when the appropriaterecharging potential is applied to the cell.

As noted above and described further below, in another embodiment of theinvention, ionomers coated on the porous catalytic electronicallyconductive support reduce or eliminate the need for ionic conductivityin the electrochemically active material.

The electrochemical reaction that occurs in a Li/water cell is a redoxreaction in which the electrochemically active cathode material getsreduced. In a Li/water cell, the catalytic electronically conductivesupport facilitates the redox reaction. As noted above, while not solimited, in a Li/water cell, the cell reaction is believed to be:

Li+H₂O=LiOH+½H₂.

The half-cell reactions at the anode and cathode are believed to be:

Anode:Li=Li⁺ +e ⁻

Cathode:e ⁻+H₂O=OH⁻ 1/2H₂

Accordingly, the catalyst for the Li/water cathode promotes electrontransfer to water, generating hydrogen and hydroxide ion. A common,inexpensive catalyst for this reaction is nickel metal; precious metalslike Pt, Pd, Ru, Au, etc. will also work but are more expensive.

Also considered to be within the scope of Li (or other activemetal)/water batteries of this invention are batteries with a protectedLi anode and an aqueous electrolyte composed of gaseous and/or solidoxidants soluble in water that can be used as active cathode materials(electrochemically active component). Use of water soluble compounds,which are stronger oxidizers than water, can significantly increasebattery energy in some applications compared to the lithium/waterbattery, where during the cell discharge reaction, electrochemicalhydrogen evolution takes place at the cathode surface. Examples of suchgaseous oxidants are O₂, SO₂ and NO₂. Also, metal nitrites, inparticular NaNO₂ and KNO₂ and metal sulfites such as Na₂SO₃ and K₂SO₃are stronger oxidants than water and can be easily dissolved in largeconcentrations. Another class of inorganic oxidants soluble in water areperoxides of lithium, sodium and potassium, as well as hydrogen peroxideH₂O₂.

The use of hydrogen peroxide as an oxidant can be especially beneficial.There are at least two ways of utilizing hydrogen peroxide in a batterycell in accordance with the present invention. First of all, chemicaldecomposition of hydrogen peroxide on the cathode surface leads toproduction of oxygen gas, which can be used as active cathode material.The second, perhaps more effective way, is based on the directelectroreduction of hydrogen peroxide on the cathode surface. Inprincipal, hydrogen peroxide can be reduced from either basic or acidicsolutions. The highest energy density can be achieved for a batteryutilizing hydrogen peroxide reduction from acidic solutions. In thiscase a cell with Li anode yields E⁰=4.82 V (for standard conditions)compared to E⁰=3.05 V for Li/Water couple. However, because of very highreactivity of both acids and hydrogen peroxide to unprotected Li, suchcell can be practically realized only for protected Li anode such as inaccordance with the present invention.

For cells using air as an electrochemically active cathode material, theair electrochemically active component of these cells includes moistureto provide water for the electrochemical reaction. The cells have anelectronically conductive support structure electrically connected withthe anode to allow electron transfer to reduce the air cathode activematerial. The electronically conductive support structure is generallyporous to allow fluid (air) flow and either catalytic or treated with acatalyst to catalyze the reduction of the cathode active material. Anaqueous electrolyte with suitable ionic conductivity or ionomer is alsoin contact with the electronically conductive support structure to allowion transport within the electronically conductive support structure tocomplete the redox reaction.

The air cathode system includes an electronically conductive component(for example, a porous electronic conductor), an ionically conductivecomponent with at least an aqueous constituent, and air as anelectrochemically active component. It may be any suitable airelectrode, including those conventionally used in metal (e.g., Zn)/airbatteries or low temperature (e.g., PEM) fuel cells. Air cathodes usedin metal/air batteries, in particular in Zn/air batteries, are describedin many sources including “Handbook of Batteries” (Linden and T. B.Reddy, McGraw-Hill, NY, Third Edition) and are usually composed ofseveral layers including an air diffusion membrane, a hydrophobic Teflonlayer, a catalyst layer, and a metal electronically conductivecomponent/current collector, such as a Ni screen. The catalyst layeralso includes an ionically conductive component/electrolyte that may beaqueous and/or ionomeric. A typical aqueous electrolyte is composed ofKOH dissolved in water. A typical ionomeric electrolyte is composed of ahydrated (water) Li ion conductive polymer such as a per-fluoro-sulfonicacid polymer film (e.g., du Pont NAFION). The air diffusion membraneadjusts the air (oxygen) flow. The hydrophobic layer preventspenetration of the cell's electrolyte into the air-diffusion membrane.This layer usually contains carbon and Teflon particles. The catalystlayer usually contains a high surface area carbon and a catalyst foracceleration of reduction of oxygen gas. Metal oxides, for example MnO₂,are used as the catalysts for oxygen reduction in most of the commercialcathodes. Alternative catalysts include metal macrocycles such as cobaltphthalocyanine, and highly dispersed precious metals such at platinumand platinum/ruthenium alloys. Since the air electrode structure ischemically isolated from the active metal electrode, the chemicalcomposition of the air electrode is not constrained by potentialreactivity with the anode active material. This can allow for the designof higher performance air electrodes using materials that would normallyattack unprotected metal electrodes.

Another type of active metal/aqueous battery cell incorporating aprotected anode and a cathode system with an aqueous component inaccordance with the present invention is a lithium (or other activemetal)/metal hydride battery. For example, lithium anodes protected witha non-aqueous interlayer architecture as described herein can bedischarged and charged in aqueous solutions suitable as electrolytes ina lithium/metal hydride battery. Suitable electrolytes provide a sourceor protons. Examples include aqueous solutions of halide acids or acidicsalts, including chloride or bromide acids or salts, for example HCl,HBr, NH₄Cl or NH₄Br.

In addition to the aqueous, air, etc., systems noted above, improvedperformance can be obtained with cathode systems incorporatingconventional Li-ion battery cathodes and electrolytes, such as metaloxide cathodes (e.g., Li_(x)CoO₂, Li_(x)NiO₂, Li_(x)Mn₂O₄ and LiFePO₄)and the binary, ternary or multicomponent mixtures of alkyl carbonatesor their mixtures with ethers as solvents for a Li metal salt (e.g.,LiPF₆, LiAsF₆ or LiBF₄); or Li metal battery cathodes (e.g., elementalsulfur or polysulfides) and electrolytes composed of organic carbonates,ethers, glymes, lactones, sulfones, sulfolane, and combinations thereof,such as EC, PC, DEC, DMC, EMC, 1,2-DME, THF, 2MeTHF, and combinationsthereof, as described, for example, in U.S. Pat. No. 6,376,123,incorporated herein by reference.

Moreover, the catholyte solution can be composed of only low viscositysolvents, such as ethers like 1,2-dimethoxy ethane (DME),tetrahydrofuran (THF), 2-methyltetrahydrofuran, 1,3-dioxolane (DIOX),4-methyldioxolane (4-MeDIOX) or organic carbonates likedimethylcarbonate (DMC), ethylmethylcarbonate (EMC), diethylcarbonate(DEC), or their mixtures. Also, super low viscosity ester solvents orco-solvents such as methyl formate and methyl acetate, which are veryreactive to unprotected Li, can be used. As is known to those skilled inthe art, ionic conductivity and diffusion rates are inverselyproportional to viscosity such that all other things being equal,battery performance improves as the viscosity of the solvent decreases.The use of such catholyte solvent systems significantly improves batteryperformance, in particular discharge and charge characteristics at lowtemperatures.

Ionic liquids may also be used in catholytes of the present invention.Ionic liquids are organic salts with melting points under 100 degrees,often even lower than room temperature. The most common ionic liquidsare imidazolium and pyridinium derivatives, but also phosphonium ortetralkylammonium compounds are also known. Ionic liquids have thedesirable attributes of high ionic conductivity, high thermal stability,no measurable vapor pressure, and non-flammability. Representative ionicliquids are 1-Ethyl-3-methylimidazolium tosylate (EMIM-Ts),1-Butyl-3-methylimidazolium octyl sulfate (BMIM-OctSO₄),1-Ethyl-3-methylimidazolium hexafluorophosphate, and1-Hexyl-3-methylimidazolium tetrafluoroborate. Although there has beensubstantial interest in ionic liquids for electrochemical applicationssuch as capacitors and batteries, they are unstable to metallic lithiumand lithiated carbon. However, protected lithium anodes as described inthis invention are isolated from direct chemical reaction, andconsequently lithium metal batteries using ionic liquids are possible asan embodiment of the present invention. Such batteries should beparticularly stable at elevated temperatures.

Safety Additives

As a safety measure, the non-aqueous interlayer architecture canincorporate a gelling/polymerizing agent that, when in contact with thereactive electrolyte (for example water), leads to the formation of animpervious polymer on the anode (e.g., lithium) surface. This safetymeasure is used for the case where the substantially impervious layer ofthe protective architecture (e.g., a glass or glass-ceramic membrane)cracks or otherwise breaks down and allows the aggressive catholyte toenter and approach the lithium electrode raising the possibility of aviolent reaction between the Li anode and aqueous catholyte.

Such a reaction can be prevented by providing in the anolyte a monomerfor a polymer that is insoluble or minimally soluble in water, forexample dioxolane (Diox) (for example, in an amount of about 5-20% byvolume) and in the catholyte a polymerization initiator for the monomer,for example, a protonic acid. A Diox based anolyte may be composed oforganic carbonates (EC, PC, DEC, DMC, EMC), ethers (1,2-DME, THF,2MeTHF, 1,3-dioxolane and others) and their mixtures. Anolyte comprisingdioxolane as a main solvent (e.g., 50-100% by volume) and Li salt, inparticular, LiAsF₆, LiBF₄, LiSO₃CF₃, LiN(SO₂C₂F₅)₂, is especiallyattractive. Diox is a good passivating agent for Li surface, and goodcycling data for Li metal has been achieved in the Diox basedelectrolytes (see, e.g., U.S. Pat. No. 5,506,068). In addition to itscompatibility with Li metal, Diox in combination with above-mentionedionic salts forms highly conductive electrolytes. A correspondingaqueous catholyte contains a polymerization initiator for Diox thatproduces a Diox polymerization product (polydioxolane) that is not or isonly minimally soluble in water.

If the membrane breaks down, the catholyte containing the dissolvedinitiator comes in direct contact with the Diox based anolyte, andpolymerization of Diox occurs next to the Li anode surface.Polydioxolane, which is a product of Diox polymerization, has highresistance, so the cell shuts down. In addition, the Polydioxolane layerformed serves as a barrier preventing reaction between the Li surfaceand the aqueous catholyte. Diox can be polymerized with protonic acidsdissolved in the catholyte. Also, the water soluble Lewis acids, inparticular benbenzoyl cation, can serve this purpose.

Thus, improvement in cyclability and safety is achieved by the use of adioxolane (Diox) based anolyte and a catholyte containing apolymerization initiator for Diox.

Active Metal Ion and Alloy Anodes

The invention pertains to batteries and other electrochemical structureshaving anodes composed of active metals, as described above. A preferredactive metal electrode is composed of lithium (Li). Suitable anolytesfor these structures and cells are described above.

The invention also pertains to electrochemical structures having activemetal ion (e.g., lithium-carbon) or active metal alloy (e.g., Li—Sn)anodes. Some structures may initially have uncharged active metal ionintercalation materials (e.g., carbon) or alloying metals (e.g., tin(Sn)) that are subsequently charged with active metal or active metalions. While the invention may be applicable to a variety of activemetals, it is described herein primarily with reference to lithium, asan example.

Carbon materials commonly used in conventional Li-ion cells, inparticular petroleum coke and mesocarbon microbead carbons, can be usedas anode materials in Li-ion aqueous battery cells. Lithium alloyscomprising one or several of the metals selected from the groupincluding Ca, Mg, Sn, Ag, Zn, Bi, Al, Cd, Ga, In and Sb, preferably Al,Sn or Si, can also be used as anode materials for such a battery. In oneparticular embodiment the anode comprises Li, Cu and Sn.

Anolyte for such structures can incorporate supporting salts, forexample, LiPF₆, LiBF₄, LiAsF₆, LiClO₄, LiSO₃CF₃, LiN(CF₃SO₂)₂ orLiN(SO₂C₂F₅)₂ dissolved in binary or ternary mixtures of non-aqueoussolvents, for example, EC, PC, DEC, DMC, EMC, MA, MF, commonly used inconventional Li-ion cells. Gel-polymer electrolytes, for instanceelectrolytes comprising one of the above mentioned salts, a polymericbinder, such as PVdF, PVdF-HFP copolymer, PAN or PEO, and a plasticizer(solvent) such as EC, PC, DEC, DMC, EMC, THF, 2MeTHF, 1,2-DME and theirmixtures, also can be used.

For batteries using these anodes, a suitable cathode structure may beadded to the electrochemical structure on the other side of theprotective architecture. The architecture enables Li-ion type cellsusing a number of exotic cathodes such as air, water, metal hydrides ormetal oxides. For Li-ion aqueous battery cells, for example, aqueouscatholyte can be basic, acidic or neutral and contains Li cations. Oneexample of a suitable aqueous catholyte is 2 M LiCl, 1 M HCl.

During the first charge of the battery with lithium-carbon lithium alloyanode, Li cations are transported from the catholyte through theprotective architecture (including the anolyte) to the anode surfacewhere the intercalation process takes place as in conventional Li-ioncells. In one embodiment, the anode is chemically or electrochemicallylithiated ex-situ before cell assembly.

Cell Designs

Electrochemical structures and battery cells in accordance with thepresent invention may have any suitable geometry. For example, planargeometries may be achieved by stacking planar layers of the variouscomponents of the structures or cells (anode, interlayer, cathode, etc.)according to known battery cell fabrication techniques that are readilyadaptable to the present invention given the description of thestructure or cell components provided herein. These stacked layers maybe configured as prismatic structures or cells.

Alternatively, the use of tubular glass or glass-ceramic electrolyteswith a non-aqueous interlayer architecture allows for the constructionof high surface area anodes with low seal area. As opposed to flat-platedesign where the seal length increases with cell surface area, tubularconstruction utilizes an end seal where the length of the tube can beincreased to boost surface area while the seal area is invariant. Thisallows for the construction of high surface area Li/water and Li/aircells that should have correspondingly high power density.

The use of a non-aqueous interlayer architecture in accordance with thepresent invention facilitates construction. An open-ended (with a seal)or close-ended glass or glass-ceramic (i.e., substantially imperviousactive metal ion conductive solid electrolyte) tube is partially filledwith a non-aqueous organic electrolyte (anolyte or transfer electrolyte)as described above, for example such as is typically used in lithiumprimary batteries A lithium metal rod surrounded by some type ofphysical separator (e.g., a semi-permeable polymer film such as Celgard,Tonin, polypropylene mesh, etc.) having a current collector is insertedinto the tube. A simple epoxy seal, glass-to-metal seal, or otherappropriate seal is used to physically isolate the lithium from theenvironment.

The protected anode can then be inserted in a cylindrical air electrodeto make a cylindrical cell, as shown in FIG. 3A. Or an array of anodesmight be inserted into a prismatic air electrode, as shown in FIG. 3B.

This technology can also be used to build Li/water, Li/metal hydride orLi/metal oxide cells by substituting the air electrode with suitableaqueous, metal hydride or metal oxide cathode systems, as describedherein above.

In addition to the use of lithium metal rods or wires (in capillarytubes), this invention can also be used to isolate a rechargeableLiC_(X) anode from aqueous or otherwise corrosive environments. In thiscase, appropriate anolyte (transfer electrolyte) solvents are used inthe tubular anode to form a passive film on the lithiated carbonelectrode. This would allow the construction of high surface area Li-iontype cells using a number of exotic cathodes such as air, water, metalhydrides or metal oxides, for example, as shown in FIG. 3C.

EXAMPLES

The following examples provide details illustrating advantageousproperties of Li metal and Li-ion aqueous battery cells in accordancewith the present invention. These examples are provided to exemplify andmore clearly illustrate aspects of the present invention and in no wayintended to be limiting.

Example 1 Li/Seawater Cell

A series of experiments was performed in which the commercial ionicallyconductive glass-ceramic from OHARA Corporation was used as a membraneseparating aqueous catholyte and non-aqueous anolyte. The cell structurewas Li/non-aqueous electrolyte/glass-ceramic/aqueous electrolyte/Pt. Alithium foil from Chemetall Foote Corporation with thickness of 125microns was used as the anode. The GLASS-CERAMIC plates were in therange of 0.3 to 0.48 mm in thickness. The GLASS-CERAMIC plate was fittedinto an electrochemical cell by use of two o-rings such that theGLASS-CERAMIC plate was exposed to an aqueous environment from one sideand a non-aqueous environment from the other side. In this case, theaqueous electrolyte comprised an artificial seawater prepared with 35ppt of “Instant Ocean” from Aquarium Systems, Inc. The conductivity ofthe seawater was determined to be 4.5 10⁻² S/cm. A microporous Celgardseparator placed on the other side of the GLASS-CERAMIC was filled withnon-aqueous electrolyte comprised of 1 M LiPF₆ dissolved in propylenecarbonate. The loading volume of the nonaqueous electrolyte was 0.25 mlper 1 cm² of Li electrode surface. A platinum counter electrodecompletely immersed in the sea water catholyte was used to facilitatehydrogen reduction when the battery circuit was completed. An Ag/AgClreference electrode was used to control potential of the Li anode in thecell. Measured values were recalculated into potentials in the StandardHydrogen Electrode (SHE) scale. An open circuit potential (OCP) of 3.05volts corresponding closely to the thermodynamic potential differencebetween Li/Li⁺ and H₂/H⁺ in water was observed (FIG. 4). When thecircuit was closed, hydrogen evolution was seen immediately at the Ptelectrode, which was indicative of the anode and cathode electrodereactions in the cell, 2Li=2Li+2e⁻ and 2H⁺+2e⁻=H₂. The potential-timecurve for Li anodic dissolution at a discharge rate of 0.3 mA/cm² ispresented in FIG. 2. The results indicate an operational cell with astable discharge voltage. It should be emphasized that in allexperiments using a Li anode in direct contact with seawater utilizationof Li was very poor, and such batteries could not be used at all at lowand moderate current densities similar to those used in this example dueto the extremely high rate of Li corrosion in seawater (over 19 A/cm²).

Example 2 Li/Air Cell

The cell structure was similar to that in the previous example, butinstead of a Pt electrode completely immersed in the electrolyte, thisexperimental cell had an air electrode made for commercial Zn/Airbatteries. An aqueous electrolyte used was 1 M LiOH. A Li anode and anon-aqueous electrolyte were the same as described in the previousexample.

An open circuit potential of 3.2 V was observed for this cell. FIG. 5shows discharge voltage-time curve at discharge rate of 0.3 mA/cm². Thecell exhibited discharge voltage of 2.8-2.9 V. for more than 14 hrs.This result shows that good performance can be achieved for Li/air cellswith solid electrolyte membrane separating aqueous catholyte andnon-aqueous anolyte.

Example 3 Li-Ion Cell

In these experiments the commercial ionically conductive glass-ceramicfrom OHARA Corporation was used as a membrane separating aqueouscatholyte and non-aqueous anolyte. The cell structure wascarbon/non-aqueous electrolyte/glass-ceramic plate/aqueouselectrolyte/Pt. A commercial carbon electrode on copper substratecomprising a synthetic graphite similar to carbon electrodes commonlyused in lithium-ion batteries was used as the anode. The thickness ofthe glass-ceramic plate was 0.3 mm. The glass-ceramic plate was fittedinto an electrochemical cell by use of two o-rings such that theglass-ceramic plate was exposed to an aqueous environment from one sideand a non-aqueous environment from the other side. The aqueouselectrolyte comprised 2 M LiCl and 1 M HCl. Two layers of microporousCelgard separator placed on the other side of the glass-ceramic werefilled with non-aqueous electrolyte comprised of 1 M LiPF₆ dissolved inthe mixture of ethylene carbonate and dimethyl carbonate (1:1 byvolume). A lithium wire reference electrode was placed between twolayers of Celgard separator in order to control the potential of thecarbon anode during cycling. A platinum mesh completely immersed in the2 M LiCl, 1 M HCl solution was used as the cell cathode. An Ag/AgClreference electrode placed in the aqueous electrolyte was used tocontrol potential of the carbon electrode and voltage drop across theGLASS-CERAMIC plate, as well as potential of the Pt cathode duringcycling. An open circuit voltage (OCV) around 1 volt was observed forthis cell. The voltage difference of 3.2 volts between Li referenceelectrode and Ag/AgCl reference electrode closely corresponding to thethermodynamical value was observed. The cell was charged at 0.1 mA/cm2until the carbon electrode potential reached 5 mV vs. Li referenceelectrode, and then at 0.05 mA/cm² using the same cutoff potential. Thedischarge rate was 0.1 mA/cm², and discharge cutoff potential for thecarbon anode was 1.8 V vs. Li reference electrode. The data in FIG. 6show that the cell with intercalation carbon anode and aqueouselectrolyte containing Li cations can work reversibly. This is the firstknown example where aqueous solution has been used in Li-ion cellinstead of solid lithiated oxide cathode as a source of Li ions forcharging of the carbon anode.

Alternative Embodiment Li/Water Battery and Hydrogen Generator for FuelCell

The use of protective architecture on active metal electrodes inaccordance with the present invention allows the construction of activemetal/water batteries that have negligible corrosion currents, describedabove. The Li/water battery has a very high theoretical energy densityof 8450 Wh/kg. The cell reaction is Li+H₂O=LiOH+½H₂. Although thehydrogen produced by the cell reaction is typically lost, in thisembodiment of the present invention it is used to provide fuel for anambient temperature fuel cell. The hydrogen produced can be either feddirectly into the fuel cell or it can be used to recharge a metalhydride alloy for later use in a fuel cell. At least one company,Millenium Cell <<http://www.millenniumcell.com/news/tech.html>> makesuse of the reaction of sodium borohydride with water to producehydrogen. However, this reaction requires the use of a catalyst, and theenergy produced from the chemical reaction of NaBH₄ and water is lost asheat.

NaBH₄+2H₂O →>4H₂+NaBO₂

When combined with the fuel cell reaction, H₂+O₂=H₂O, the full cellreaction is believed to be:

NaBH₄+2O₂→2H₂O+NaBO₂

The energy density for this system can be calculated from the equivalentweight of the NaBH₄ reactant (38/4=9.5 grams/equiv.). The gravimetriccapacity of NaBH₄ is 2820 mAh/g; since the voltage of the cell is about1, the specific energy of this system is 2820 Wh/kg. If one calculatesthe energy density based on the end product NaBO₂, the energy density islower, about 1620 Wh/kg.

In the case of the Li/water cell, the hydrogen generation proceeds by anelectrochemical reaction believed described by:

Li+H₂O=LiOH+½H₂

In this case, the energy of the chemical reaction is converted toelectrical energy in a 3 volt cell, followed by conversion of thehydrogen to water in a fuel cell, giving an overall cell reactionbelieved described by:

Li+½H₂O+¼O₂=LiOH

where all the chemical energy is theoretically converted to electricalenergy. The energy density based on the lithium anode is 3830 mAh/g at acell potential of about 3 volts which is 11,500 Wh/kg (4 times higherthan NaBH₄). If one includes the weight of water needed for thereaction, the energy density is then 5030 Wh/kg. If the energy densityis based on the weight of the discharge product, LiOH, it is then 3500Wh/kg, or twice the energy density of the NaBO₂ system. This can becompared to previous concepts where the reaction of lithium metal withwater to produce hydrogen has also been considered. In that scenario theenergy density is lowered by a factor of three, since the majority ofthe energy in the Li/H₂O reaction is wasted as heat, and the energydensity is based on a cell potential for the H₂/O₂ couple (as opposed to3 for Li/H₂O) which in practice is less than one. In this embodiment ofthe present invention, illustrated in FIG. 7, the production of hydrogencan also be carefully controlled by load across the Li/water battery,the Li/water battery has a long shelf life due to the protectivemembrane, and the hydrogen leaving the cell is already humidified foruse in the H₂/air fuel cell.

CONCLUSION

Although the foregoing invention has been described in some detail forpurposes of clarity of understanding, it will be apparent that certainchanges and modifications may be practiced within the scope of theinvention. In particular, while the invention is primarily describedwith reference to a lithium metal, alloy or intercalation anode, theanode may also be composed of any active metal, in particular, otheralkali metals, such as sodium. It should be noted that there are manyalternative ways of implementing both the process and compositions ofthe present invention. Accordingly, the present embodiments are to beconsidered as illustrative and not restrictive, and the invention is notto be limited to the details given herein.

All references cited herein are incorporated by reference for allpurposes.

1. An electrochemical cell structure, comprising: an anode comprising amaterial selected from the group consisting of an active metal, activemetal-ion, active metal alloy, active metal alloying metal or activemetal intercalating material; and an ionically conductive protectivearchitecture on a first surface of the anode, the architecturecomprising, an active metal ion conducting separator layer comprising asemi-permeable polymer membrane comprising a non-aqueous anolyte, theseparator layer being chemically compatible with the active metal, andin contact with the anode, and a substantially impervious ionicallyconductive layer chemically compatible with the separator layer, and incontact with the separator layer.
 2. The structure of claim 1, whereinthe anolyte is in the liquid phase.
 3. The structure of claim 1, whereinthe anolyte is in the gel phase.
 4. The structure of claim 1, whereinthe substantially impervious ionically conductive layer comprises amaterial selected from the group consisting of glassy or amorphousactive metal ion conductors, ceramic active metal ion conductors, andglass-ceramic active metal ion conductors.
 5. The structure of claim 4,wherein substantially impervious ionically conductive layer is an ionconductive glass-ceramic having the following composition: Compositionmol % P₂O₅ 26-55% SiO₂ 0-15% GeO₂ + TiO₂ 25-50% in which GeO₂ 0-50% TiO₂0-50% ZrO₂ 0-10% M₂O₃ 0-0% Al₂O₃ 0-15% Ga₂O₃ 0-15% Li₂O 3-25%

and containing a predominant crystalline phase composed ofLi_(1+x)(M,Al,Ga)_(x)(Ge_(1−y)Ti_(y))_(2−x)(PO₄)₃ where X≦0.8 and0≦Y≦1.0, and where M is an element selected from the group consisting ofNd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb, and/orLi_(1+x+y)Q_(x)Ti_(2−x)Si_(y)P_(3−y)O₁₂ where 0<X≦0.4 and 0<Y≦0.6, andwhere Q is Al or Ga.
 6. The structure of claim 1, wherein the protectivearchitecture has an ionic conductivity of at least 10⁻⁴ S/cm.
 7. Thestructure of claim 1, wherein the active metal anode is selected fromthe group consisting of lithium metal, lithium metal alloy and lithiumintercalation material.
 8. The structure of claim 7, wherein the activemetal anode is lithium metal.
 9. The structure of claim 1, wherein theanode comprises lithium metal-ions.
 10. The structure of claim 1,wherein the anode comprises lithium metal alloying metal.
 11. Thestructure of claim 10, wherein the lithium metal alloying metal isselected from the group consisting of Ca, Mg, Sn, Ag, Zn, Bi, Al, Cd,Ga, In and Sb.
 12. The structure of claim 1, wherein the anode compriseslithium metal intercalating material.
 13. The structure of claim 12,wherein the lithium metal intercalating material comprises carbon.
 14. Abattery cell, comprising: an electrochemical cell structure inaccordance with claim 1; and a cathode structure.
 15. The cell of claim14, wherein the cathode structure comprises a catholyte selected fromthe group consisting of aqueous and non-aqueous electrolytes.
 16. Thecell of claim 15, wherein the cathode structure further compriseselectrochemically active material selected from the group consisting ofsolid, liquid and gaseous oxidizers.
 17. The cell of claim 14, whereinthe cathode structure comprises seawater.
 18. The cell of claim 14,wherein the cathode structure comprises an air electrode.
 19. The cellof claim 14, wherein the cathode structure comprises an ionic liquid.20. The cell of claim 14, wherein the active metal anode is lithiummetal.
 21. The cell of claim 14, wherein the anode comprises lithiummetal-ions.
 22. The cell of claim 14, wherein the anode compriseslithium metal alloying metal.
 23. The cell of claim 14, wherein theanode comprises lithium metal intercalating material.
 24. The cell ofclaim 22 wherein the lithium metal intercalating material comprisescarbon.
 25. The cell of claim 14, wherein the anolyte is in the liquidphase.
 26. The cell of claim 14, wherein the anolyte is in the gelphase.
 27. The cell of claim 14, wherein the substantially imperviousionically conductive layer comprises a material selected from the groupconsisting of glassy or amorphous active metal ion conductors, ceramicactive metal ion conductors, and glass-ceramic active metal ionconductors.
 28. The structure of claim 22, wherein substantiallyimpervious ionically conductive layer is an ion conductive glass-ceramichaving the following composition: Composition mol % P₂O₅ 26-55% SiO₂0-15% GeO₂ + TiO₂ 25-50% in which GeO₂ 0-50% TiO₂ 0-50% ZrO₂ 0-10% M₂O₃0-0% Al₂O₃ 0-15% Ga₂O₃ 0-15% Li₂O 3-25%

and containing a predominant crystalline phase composed ofLi_(1+x)(M,Al,Ga)_(x)(Ge_(1−y)Ti_(y))_(2−x)(PO₄)₃ where X<0.8 and0≦Y≦1.0, and where M is an element selected from the group consisting ofNd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb, and/orLi_(1+x+y)Q_(x)Ti_(2−x)Si_(y)P_(3−y)O₁₂ where 0<X≦0.4 and 0<Y≦0.6, andwhere Q is Al or Ga.
 29. The cell of claim 14, wherein the protectivearchitecture has an ionic conductivity of at least 10⁻⁴ S/cm.